Reference is hereby made to the following, commonly assigned, co-pending, U.S. Patent Applications which disclose common subject matter: Ser. No. 09/067,729 filed Apr. 28, 1998 for MULTIPLE CHANNEL, SEQUENTIAL, CARDIAC PACING SYSTEMS filed in the names of C. Struble et al.; Serial No. 09/439,244 filed on event date herewith for MULTI-SITE CARDIAC PACING SYSTEM HAVING CONDITIONAL REFRACTORY PERIOD filed in the names of K. Kleckner et al.; Serial No. 09/439,078 filed on even date herewith for MULTI-SITE CARDIAC PACING SYSTEM HAVING TRIGGER PACE WINDOW in the names of C. Juran et al.; Serial No. 09/439,569 filed on even date herewith for CARDIAC PACING SYSTEM DELIVERING MULTI-SITE PACING IN A PREDETERMINED SEQUENCE TRIGGERED BY A SENSE EVENT in the names of C. Yerich et al.; Serial No. 09/439,568 filed on even date herewith for RECHARGE CIRCUITRY FOR MULTI-SITE STIMULATION OF BODY TISSUE filed in the names of B. Blow et al.; and Serial No. 09/439,243 filed on even date herewith for AV SYNCHRONOUS CARDIAC PACING SYSTEM DELIVERING MULTI-SITE VENTRICULAR PACING TRIGGERED BY A VENTRICULAR SENSE EVENT DURING THE AV DELAY in the names of C. Yerich et al.
The present invention pertains to multi-site cardiac pacing systems for pacing right and left heart chambers in inhibited and triggered pacing modes employing combinations of right and left heart chamber pace/sense electrodes for providing left heart chamber pacing and sensing to facilitate placement of the left heart chamber pace/sense electrode at a left heart chamber pace/sense site that is difficult to access.
In diseased hearts having conduction defects and in congestive heart failure (CHF), cardiac depolarizations that naturally occur in one upper or lower heart chamber are not conducted in a timely fashion either within the heart chamber or to the other upper or lower heart chamber. In patients suffering from CHF, the hearts may become dilated, and the conduction and depolarization sequences of the heart chambers may exhibit Intra-Atrial Conduction Defects (IACD), Left Bundle Branch Block (LBBB), Right Bundle Branch Block (RBBB), and Intra Ventricular Conduction Defects (IVCD). In such cases, the right and left heart chambers do not contract in optimum synchrony with each other, and cardiac output suffers due to the conduction defects. In addition, spontaneous depolarizations of the left atrium or left ventricle occur at ectopic foci in these left heart chambers, and the natural activation sequence is grossly disturbed. In such cases, cardiac output deteriorates because the contractions of the right and left heart chambers are not synchronized sufficiently to eject blood therefrom. Furthermore, significant conduction disturbances between the right and left atria can result in left atrial flutter or fibrillation.
It has been proposed that various conduction disturbances involving both bradycardia and tachycardia of a heart chamber could benefit from pacing pulses applied at multiple electrode sites positioned in or about a single heart chamber or in the right and left heart chambers in synchrony with a depolarization which has been sensed at a minimum of at least one of the electrode sites. It is believed that cardiac output can be significantly improved when left and right chamber synchrony is restored, particularly in patients suffering from dilated cardiomyopathy and CHF.
A number of proposals have been advanced for providing pacing therapies to alleviate these conditions and restore synchronous depolarization and contraction of a single heart chamber or right and left, upper and lower, heart chambers as described in detail in commonly assigned U.S. Pat. Nos. 5,403,356, 5,797,970 and 5,902,324 and in 5,720,768 and 5,792,203 all incorporated herein by reference. The proposals appearing in U.S. Pat. Nos. 3,937,226, 4,088,140, 4,548,203, 4,458,677, 4,332,259 are summarized in U.S. Pat. Nos. 4,928,688 and 5,674,259, all incorporated herein by reference. The advantages of providing sensing at pace/sense electrodes located in both the right and left heart chambers is addressed in the ""688 and ""259 patents, as well as in U.S. Pat. Nos. 4,354,497, 5,174,289, 5,267,560, 5,514,161, and 5,584,867, also all incorporated herein by reference.
The medical literature also discloses a number of approaches of providing bi-atrial and/or bi-ventricular pacing as set forth in: Daubert et al., xe2x80x9cPermanent Dual Atrium Pacing in Major Intra-atrial Conduction Blocks: A Four Years Experiencexe2x80x9d, PACE (Vol.16, Part II, NASPE Abstract 141, p.885, April 1993); Daubert et al., xe2x80x9cPermanent Left Ventricular Pacing With Transvenous Leads Inserted Into The Coronary Veinsxe2x80x9d, PACE (Vol. 21, Part II, pp. 239-245, January 1998); Cazeau et al., xe2x80x9cFour Chamber Pacing in Dilated Cardiomyopathyxe2x80x9d, PACE (Vol. 17, Part II, pp. 1974-1979, November 1994); and Daubert et al., xe2x80x9cRenewal of Permanent Left Atrial Pacing via the Coronary Sinusxe2x80x9d, PACE (Vol. 15, Part II, NASPE Abstract 255, p. 572, April 1992), all incorporated herein by reference.
In the above-incorporated ""768 patent, bipolar right heart chamber leads and unipolar left heart chamber leads are employed. Sensing of right heart depolarizations of the right heart chamber is effected between right heart chamber active tip and indifferent ring electrodes on the bipolar right heart lead. Sensing of the left heart chamber depolarizations is effected between a single left heart chamber active tip pace/sense electrode and the right heart chamber active tip pace/sense electrode. Then, sensing is switched to a unipolar mode to determine the true chamber of origin of the sensed left heart depolarization. Right and left heart chamber pacing to the other heart chamber is effected in a unipolar manner, employing the IPG housing or canister as an indifferent IPG xe2x80x9ccanxe2x80x9d electrode.
In the above-incorporated ""970 patent, bipolar left and right heart chamber pacing leads are employed that are coupled to a single sense amplifier and pacing output amplifier for sensing right and left heart depolarizations and providing right and left heart chamber pacing pulses. When sensing, the right and left heart chamber active tip pace/sense electrodes are coupled together to one input of the sense amplifier, and the right and left heart chamber indifferent ring pace/sense electrodes are coupled together to the other input of the sense amplifier. When pacing the right heart chamber, the right and left heart chamber indifferent ring pace/sense electrodes are coupled together, and a low energy pacing pulse is delivered through the right heart chamber active tip electrode. When pacing the left heart chamber, the right and left heart chamber indifferent ring pace/sense electrodes are coupled together, and a high energy pacing pulse is delivered through both the right and left heart chamber active tip electrodes. The pacing pulse energy is distributed along multiple pacing vectors, and in fact both the right and left heart chambers are simultaneously paced.
It is important that pacing energy be directed in a vector that maximizes efficiency of capturing the heart. In addition, the location of a left ventricular distal active pace/sense electrode deep in a cardiac vein within the narrow vessel lumen necessitates use of very small diameter unipolar lead bodies that do not allow inclusion of an indifferent ring electrode and associated lead conductor and insulation separating it from the lead conductor for the active pace/sense electrode. Since the active pace/sense electrode is separated from direct contact with the left ventricular myocardium, the left ventricular pacing threshold is likely to be higher than the right ventricular pacing threshold requiring a higher energy left ventricular pacing pulse than right ventricular pacing pulse. It is desirable to direct the left ventricle pacing pulse in a left ventricular pacing vector that traverses as great a bulk of the left ventricular myocardial mass as possible. It is undesirable to dissipate that pacing pulse energy in the right ventricle as is the case in approach disclosed in the ""970 patent or to direct it through a vector traversing only a portion of the left ventricle to the remotely located indifferent IPG can electrode as is the case in the unipolar pacing modes disclosed in the above-incorporated ""768 patent.
In the case of bi-atrial pacing systems, it is also desirable to direct the left atrial pacing pulse in an efficient left atrial pacing vector and to not dissipate pacing energy in body tissue or in the right atrium.
The present invention is therefore directed to providing right and left heart chamber pacing systems and methods of operation that provide efficient pacing of the left heart chamber without dissipating left heart chamber pacing energy.
In a bi-chamber pacing system, an IPG optionally having an indifferent IPG can electrode is coupled to a small diameter, unipolar, left heart chamber (LHC) endocardial lead and a bipolar right heart chamber (RHC) endocardial lead. The LHC lead is advanced through a venous pathway to locate the LHC active pace/sense electrode at a desired LHC pace/sense site. The RHC lead is advanced into the RHC chamber to locate RHC active and indifferent pace/sense electrodes therein. Sensing of RHC spontaneous cardiac depolarizations to provide a RHC sense event signal and delivery of RHC pacing pulses is conducted across the RHC active pace/sense electrode and one of the RHC or IPG indifferent pace/sense electrodes. Sensing of LHC spontaneous cardiac depolarizations to provide a LHC sense event signal is conducted across the LHC active pace/sense electrode and one of the RHC active or indifferent pace/sense electrodes or the IPG indifferent can electrode. Delivery of LHC pacing pulses is conducted across the LHC active pace/sense electrode and the RHC indifferent pace/sense electrode, whereby the LHC pacing vector traverses the mass of the LHC.
In a bi-ventricular pacing system, a small diameter, unipolar, left ventricular, coronary sinus (LV CS) endocardial lead and a bipolar right ventricular (RV) endocardial lead are preferably employed to provide the LHC and RHC pace/sense electrodes. The LV CS lead is advanced through the superior vena cava, the right atrium, the ostium of the coronary sinus (CS), the CS, and into a coronary vein descending from the CS to locate the LV active pace/sense electrode at a desired LV pace/sense site. The RV lead is advanced into the RV chamber to locate RV active and indifferent pace/sense electrodes therein. Sensing of RV spontaneous cardiac depolarizations to provide a RV sense event signal and delivery of RV pacing pulses is conducted across the RV active pace/sense electrode and one of the RV or IPG indifferent pace/sense electrodes. Sensing of LV spontaneous cardiac depolarizations to provide a LV sense event signal is conducted in a unipolar sensing vector across the LV active pace/sense electrode and the IPG indifferent pace/sense electrode or in a trans-ventricular sensing vector across the LV active pace/sense electrode and one of the RV active or indifferent pace/sense electrodes. Delivery of LV pacing pulses is conducted across the LV active pace/sense electrode and the RV indifferent pace/sense electrode and in a pacing vector that encompasses the bulk of the LV.
In a bi-atrial pacing system, a unipolar, left atrial, coronary sinus (LA CS) lead and a bipolar right atrial (RA) endocardial lead are preferably employed to provide the LHC and RHC pace/sense electrodes. Use of epicardial leads is of course an option. The unipolar LA CS(or epicardial) lead locates an active LA pace/sense electrode in relation to the LA, and the bipolar RA lead locates an active RA pace/sense electrode and indifferent RA pace/sense electrode in relation to the RA. Sensing of LA spontaneous cardiac depolarizations to provide a LA sense event signal is conducted across the LA active pace/sense electrode and one of the RA active or indifferent pace/sense electrodes or the IPG indifferent pace/sense electrodes. Delivery of LA pacing pulses is conducted across the LA active pace/sense electrode and the RA indifferent pace/sense electrode and in a pacing vector that encompasses the bulk of the LA.
In the context of bi-atrial or bi-ventricular pacing systems and methods, a number of triggered pacing modes are possible. In one triggered pacing mode, a first pacing pulse can be delivered to the RHC or LHC and a second pacing pulse delivered to the LHC or RHC, respectively, after a triggered pacing delay. The two pacing pulses can be delivered either upon a non-refractory sense event detected in one of the heart chambers or upon timeout of a pacing escape interval. Alternatively, following a non-refractory sense event in the RHC or LHC, a single pacing pulse can be delivered to the LHC or RHC, respectively after time-out of the triggered pacing delay timed from the sense event. In still another triggered pacing mode, a single pacing pulse can be delivered to the RHC or LHC where the non-refractory sense event is detected.
The present invention is preferably implemented in systems for providing atrial or ventricular bi-chamber pacing or AV synchronous pacing systems for providing three or four chamber pacing.
The present invention is also preferably implemented into an external or implantable pulse generator and lead system selectively employing right and left heart, atrial and/or ventricular leads. The preferred embodiment is implemented in an architecture that allows wide programming flexibility for operating in AV synchronous modes with right and left ventricular pacing or in atrial or ventricular only modes for providing only right and left atrial or ventricular pacing. The AV synchronous embodiments may be implemented into an IPG or external pulse generator and lead system providing right and left ventricular pacing and sensing and either both right and left atrial pacing or just right or left atrial pacing and sensing. Alternatively, the invention can be implemented in IPGs or external pulse generators and lead systems having hard wired connections and operating modes that are not as programmable.